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TURN LANE DESIGN CHECKLIST (PAGE 1 OF 2)� STEP 3 — CALCULATE TURN LANE DEMAND Deceleration Based on speed and facility type determine deceleration length for turn lane. Deceleration Distance Length a Table B-1 for low speed (20 — 50 mph) Urban Conventional Roadway Page 8-1 0 Table B-2 for high speed (45 — 75 mph) Rural and Urban Roadways feet I Interpolation between values in the tables may be necessary based on speed data. Storage Length Unsignalized Intersections Storage Page 3-12 Left Turn Lane — see Table B-3, based on Left -Turning Volume and Heavy Commercial Distance or equation on Page B-12. Right Turn Lane — assumed to be 0 feet since in virtually all cases these vehicles would have the right-of-way entering the intersection and would incur no delay Signalized intersections ❑ Synchro Output Available: 951h percentile queue length. ❑ Method 1 — Basic Equation: equation on Page B-13. El Method 2 — Look Up Tables: Tables B-4 through B-6 on Page B-14 using Sum of 1 feet Critical Movement Calculations see Page 4 of checklist_) { _ Turn Lane Turn Lane Demand Demand Add the Deceleration Distance and the Storage Distance _ /Ofeet STEP 4 — CALCULATE TURN LANE DESIGN Determine Determine Taper based on Facility Type I Taper Length g 8-1, El Unconstrained Conventional/Expressway = 1$0 feet (1:15 taper) fPagPe ❑ Constrained Expressway = 100 feet (1:8 taper) ❑ Constrained Conventional = 60 feet (1:5 taper) %„ 4J feet I Full Turn Lane _ - Take the Turn Lane Demand minus Taper Length Full Width Turn Lane ' Length (before Length (no adjustments) adjustments) I rb feet Adjust Taper Pane 3-2' Adjust Full turn Lane Length I I ADJUSTMENTS AND FINAL TURN LANE DESIGN If the intersection is located on a horizontal curve, use a 1:8 taper (100 feet) If grade is greater than 3% adjust based on Table B-9 (multiply the Deceleration Distance by adjustment in table and document the + r difference in deceleration to the right. Page 9- 19 ft If heavy commercial is greater than averages shown in Table B-10, increase Deceleration Distance by 30% and document the difference in length to the right. Pape 3-20 — Are there more than 300 vehicles per hour? May consider dual lefts. The storage length required would be half of the calculated Storage Distance. Document the difference in distance to the right. Page 3-22 Are there constraints with the adjacent intersections or driveways? Does the through lane queue extend further than the turn lane length? Document a review of the potential impact to the desired turn lane length and adjust accordingly. Page 3-2,' t P-24 Total Adit;stment-s ft ft ft ft Adjusted Taper Length 0 feet Full Width Turn Lane Length (with adjustments) / 5% feet Development of Turn Lane Design Guidelines